Lockheed Martin is completing preliminary design of a low-boom flight demonstrator as part of NASA’s Quiet Supersonic Transport (QueSST) project. The single-engine, Mach 1.4+ X-plane is intended to mimic the shockwave signature of a 100- to 120-seat supersonic airliner and show that a shaped sonic boom of 75 PLdB is quiet enough to permit supersonic flight over land. NASA plans to fly the competitively procured X-plane in 2019 and begin community acceptance testing in 2020.

The ability to fly supersonic over land will be the game changer for supersonic business jets, but that’s not likely to happen for another 10 to 15 years, says Gulfstream, which is actively but quietly studying the concept.

“The earliest will be 2025-2030,” says Dan Nale, SVP for programs, engineering and test. “That’s the earliest the ICAO process can change the rules to allow it.” Meanwhile Gulfstream, which has conducted more studies into supersonic flight and mitigation of the sonic boom than any other business jet manufacturer, continues to carry out original research, participate in regulatory issues and undertake paper studies.

“We’re doing a lot of the preliminary design studies,” says Nale, who believes the sonic boom and engine emissions from flying that fast at altitude will be the two major issues to overcome. Next step is for NASA to fly its proposed supersonic demonstrator, on which it is working with Lockheed Martin. “Gulfstream is involved as part of NASA’s consulting review panel,” he adds.

Gulfstream believes the aircraft must be shaped to minimize the boom, and to that end it earlier test-flew an extending nose on a NASA F-15. That Pinocchio-like proboscis is now on display in the lobby of the company’s advanced acoustics lab in Savannah.